[Often] function and often target

#include<iostream>
using namespace std;

class A{
	private:
		int num1;            //常函数不可修改
		mutable int num2;    //常函数可修改 
		
	public:
		//常函数：在函数后面加上const 
		void fun1() const{     //常对象可调用 
			num2 = 100;    
		}
		void fun2() {          //常对象可调用
			num1 = 100;    
		}
		
		A(int n1,int n2){
			num1 = n1;
			num2 = n2;
		}
};

int main(){
	//常对象：声明对象前加const 
	const A a(10,20); 
	a.fun1();   //常对象调用常函数 
	return 0;
}